Stabilized extreme pressure lubricant



United States Patent 2,704,745 STABILIZED EXTREME PRESSURE LUBRICANT Harry L. Kopp, Alexandria, Va., and Leo W. Manley, Woodbury, N. 1., assignors to Socony-Vacuum Oil Company, Incorporated, a corporation of New York No Drawing. Application February 1, 1954, Serial No. 407,574

7 Claims. (Cl. 252-372) This invention relates to the art of lubrication and is particularly concerned with lubricants suitable for use under abnormally high pressures, such as are encountered between engaged surfaces in various types of modern industrial machinery, such as the worm gears and the like. The so-called extreme pressure lubricants with which this invention is concerned comprise a mineral lubricating oil having dissolved or dispersed therein one or more chemical agents which will provide between the engaged surfaces a lubricating film capable of withstanding high pressures. The invention is spec fically concerned with extreme pressurt lubricants of this type which possess high oxidation stability.

It was recognized in the past that the presence of sulfur or sulfur-containing compounds in a lubricating 011 enhanced the load-carrying ability of the 011. Thus, for example, Smackover Black Oil, an unrefined residuum stock of high-sulfur content, was known to possess good extreme pressure properties. Later, it was found that the load-carrying ability of such high-sulfur oils could be greatly improved by the incorporation therem of certain heavy metal soaps. Lead naphthenate, for example, was found to be outstandingly elfective in this respect. A serious drawback, however, with respect to the use of lead naphthenate was that it reduced the oxidat on stability of the oil. The degree of oxidation stab1l1ty 1s manifested by the rate of increase in viscosrty of the 011 m use, an oil which is highly unstable becoming quite VlS- cous in a relatively short time.

It was later found that the oxidation stability of compositions containing lead naphthenate could be greatly improved without diminishing their extreme pressure ability by utilizing a synthetic sulfur compound, such as dibenzyl disulfide, as a source of sulfur along with a relatively stable base oil rather than using relatively unstable high sulfur content base oils, per se. Thus, the oils used in these compositions were oils which had been refined to remove unstable components thereof. A considerable variety of organic sulfur-contaming compounds have been utilized in combination with lead naphthenate in oils of this type. For example, a typical chemical extreme pressure composition employs dibenzyl dlSlllfide and lead naphthenate in a Pennsylvania cyhnder type oil.

We have now found that the oxidation stability of extreme pressure compositions of the last-defined type can be improved even further, and without impa1rment of their extreme pressure character, by utilizing as the synthetic extreme pressure agent an organic compound containing both sulfur and nitrogen, rather than a compound containing sulfur alone.

Only certain sulfurand nitrogen-containing orgamc compounds, however, are suitable for use in the invention, since only these meet all the requirements necessary for use as an extreme pressure agent in a mineral oil type lubricant. Thus, such additives must possess the following characteristics: (1) adequate oil solubility, (2) adequate load-carrying ability, (3) relative inactivity towards copper and (4) adequate oxidation inhibition. The sulfurand nitrogen-containing compounds which have been found to meet all of these requirements are: Z-benzothiazyl N-N diethyl thio carbamyl sulfide, Z-benzothiazyl N-N dibutyl thio carbamyl sulfide, oxypentamethylene thio carbamyl diethyl thio carbamyl sulfide, bis-4-methylbenzothiazyl disulfide, benzothiazyl-N-N-butyl disulfide and benzothiazyl-tertbutyl disulfide.

It is, therefore, the object of this invention to provide extreme pressure lubricating oil compositions of superior oxidation stability, said compositions containing in com- Patented Mar. 22, 1955 "ice bination one of the aforementioned sulfurand nitrogencontaining compounds and lead naphthenate. Other and further objects will become apparent hereinafter.

As previously indicated, the base oils contemplated for use in the compositions of the invention are oils which have been refined to remove unstable components thereof, such as by solvent-refining. The oil need not be of any particular source or type and may range in viscosity from as low as seconds S. U. V. at 100 F. to as high as 500 seconds at 210 F., depending upon the application for which the lubricant is inteended. The invention, therefore, provides highly stable extreme pressure lubricating compositions comprising a refined mineral lubricating oil and minor proportions of one of the aforesaid sulfurand nitrogen-containing organic compounds and lead naphthenate.

The uniqueness of the several sulfur-and nitrogencontaining organic compounds of the invention as extreme pressure agents as compared to organic sulfurand nitrogen-containing compounds in general is shown by the data given in Table I. This table lists a number of other sulfurand nitrogen-containing organic compounds which were tested and found not suitable for failure to meet one or more of the requirements necessary for extreme pressure oil additives as mentioned hereinabove. The procedures utilized in testing these compounds were as follows:

1. The copper strip corrosion test procedure was that of A. S. T. M. Method D-50T (A. S. T. M. Standards on Petroleum Products and Lubricants, November 1952, pages 81-84).

2. The Timken test was conducted according to CRC Method L-l8-545 (CRC Handbook, 1946 edition, pages 462-466).

3 The oil solubility test was conducted by preparing hand blends of the compounds in light mineral oil and visibly observing the clarity of the blends. 4. The oxidation test sitnilates oxidation which occurs in industrial equipment, such as gear sets in which the oil is churned and intimately mixed with air. The test oil is subjected to a temperature of 250 F. and stirred with a paddle made of 2" x 2" copper and steel plates bolted together. The paddle is immersed in the oil and turned at a speed of 2051-5 R. P. M., thereby mixing air into the oil. Viscosity measurements are taken on the oil before the test, periodically during the test and at fourteen days, the end of the test. Percent increase in viscosity is determined.

The base oil used in all tests was a Pennsylvania cylinn-octyl-N,N-diethylthionourethan Do. Phenyl-N,N-diethylthionourethan Corrosive to copper. Pcntaehlorophenyl-N,N-diethylthionourethan. Poor oil-solubility. 2, l-dichlorophenyl-N,N-diethylthionone car- Corrosive to copper.

bonate. N,N-diethyl-N,N-diphenyl thiourea Inadequate load-carrying capacity. N,N'-drphenyl-r l'-diethyl thiocarbamyl-p- Poor oil-solubility.

phenylene diamme. Pentamethylene thiocarbamyldiethyl thio- Corrosive to copper.

carbamyl sulfide. Uutsllsgn-dmthyl di(2-ethoxy ethyl) thiurane Do.

s e. 2-benzothiazole-N-cyclopentamethylenc thio- Poor oil-solubility.

carbamyl sulfi e. l,3,4-lhiadiazolyl-2,5-bis(dlethyl dithiocarba- Do.

In 3-phenyl-2-thiono 4-1, 3,4-thiadiazolinyldithiooarbamate. I

' St. Louis, Missouri.

In contrast. to the sulfur-nitrogen compounds shown in Table I, the several sulfur-nitrogen compounds contemplated by the invention all proved entirely satisfactory from the standpoint of their oil-solubility and copper corrosion characteristics. In addition, these compounds provided extreme pressure lubricants of outstanding stability toward oxidation, as shown by the data in Table II. This table shows the results of extreme pressure and oxidation tests made on typical. compositions prepared usingthe several sulfur-nitrogen compounds of the invention and on a typical lubricant of the commercial type employing dibenzyl disulfide. It will be seen that in all cases the compositions contemplated by the invention showed a marked superiority to the commercial lubricant in oxidation stability; and, in all cases, except one, a marked improvemcnt'in load-carrying capacity. In no case was the load-carrying capacity below that obtained with the commercial lubricant. The Timken and oxidation test procedures in all cases were the same as those utilized in testing the compounds shown in Table I. The base oil was also the same as that used in testing the compounds listed in Table I.

Table II Oxidation Timken 3 8 7 Product Blended in on g is. In-

Lbs. 6?? Percent None 24 5% Lead Naphthenate 20 68 .5% Dibenzyl' Disulfide 35 69 5% Lead Naphthenate 0.25% Z-Benzothiazyl N-N Dlethyl Thio Car- 27 bamyl Sulfide. 50 5% Lead Naphthenate 0.5% 2-Benzothiazyl N-N Dibutyl Thro Oarbamyl Sulfide. 35 26 5% Lead Naphthenatc 0.25% Oxypentamethylene T1110 Oar-bamyl Diethyl Thio Oarbamyl Sulfide. 5O 58 5% Lead Naphthenate. 0.5% Bis-4-Methybenzoth1azyl Disulfide 45 38 5% Lead Naphthenate 0.25% Benzothiazyl-N-Butyl Drsulflde. 45 33 5% Lead Naphthenate 0.25% Benzothiazyl-Tert-Butyl Dlsulfi 45 35 5% Lead N aphthenate All of the sulfurand nitrogen-containing compounds utilized in the invention were obtained from chemical manufacturers, principally Sharples Chemicals, Inc., Wyandotte, Michigan, and Monsanto Chemical Company, They may be further identified by their chemical formulae as follows:

2-benzothiazy1 N-N diethyl thio carbamyl sulfide \S/ g cnn Z-benzothiazyl N-N dibutyl thio carbamyl sulfide Oxypentamethylene thio carbamyl diethyl thio carbamyl sulfide Bis-4-methylbenzothiazy1 disulfide Benzothiazyl-t-butyl disulflde Since these compounds are known to the art and may be prepared by a number of different methods, specific details with respect to their preparation will not be given here. Briefly, however, Z-benzothiazyl N-N diethyl thio carbamyl sulfide and 2-benzothiazyl N-N dibutyl thio carbamyl sulfide may be made by reaction of sodium mercaptobenzothiazole with N-diethyl thiono carbamyl chloride and N-dibutyl thiono carbamyl chloride, respectively. Bis-4-methylbenzothiazyl disulfide may be prepared by oxidation in an aqueous solution of sodium mercaptobenzothiazole using chlorine as the oxidizing agent. Benbzothiazyl-N-butyl and benzothiazyl tertiary butyl disulfide may be made by reaction of N-butyl disulfide and tertiary butyl disulfide, respectively, with bis-benzothiazyl disulfide in the presence of sodium sulfide and ethyl alcohol at C., and oxypentamethylene thio carbamyl diethyl thio carbamyl sulfide may be prepared by reacitiign of morphaline with diethyl amine and carbon disul- Although the specific compositions shown herein, for purposes of comparison, all contain 5 weight per cent lead naphthenate and either 0.25 or 0.5 weight per cent of the sulfur-nitrogen compound, the amount of each of these additives can be varied within reasonable limits, depending upon the particular application for which the lubricant is designed. Thus, the amount of lead naphthenate which may be used ranges from about 1 to about 20 weight per cent, while the amount of the sulfurnitrogen compound may be from about 0.1 to about 3.0 weight per cent.

Additional additives, designed to impart various other lubricating characteristics to the compositions of this invention, such as pour depressants, viscosity index improvers, etc., may be used therein, if desired.

Having now fully described the invention, what is claimed as new and patentable is:

1. A lubricant composition comprising a major proportion of a refined mineral lubricating oil and (1) from about 0.1% to about 3.0% by weight of a sulfurand nitrogen-containing organic compound selected from the group consisting of 2-benzothiazyl N-N diethyl thio carbamyl sulfide, 2-benzothiazyl N-N dibutyl thio carbamyl sulfide, oxypentamethylene thio carbamyl diethyl thio carbamyl sulfide, bis-4-methybenzothiazyl disulfide, benzothiazyl-N-butyl disulfide and benzothiazyl-tert-butyl disulfide and (2) from about 1% to about 20% by weight of lead naphthenate.

2. A lubricant composition comprising a major proportion of a refined mineral lubricating ail and (1) from about 0.1% to about 3.0% by weight of 2-benzothiazyl N-N diethyl thio carbamyl sulfide and (2) from about 1% to about 20% by weight of lead naphthenate.

3. A lubricant composition comprising a major proportion of a refined mineral lubricating oil and (1) from about 0.1% to about 3.0% by weight of Z-benzothiazyl N-N dibutyl thio carbamyl sulfide and (2) from about 1% to about 20% by weight of lead naphthenate.

4. A lubricant composition comprising a major proportion of a refined mineral lubricating oil and (1) from about 0.1% to about 3.0% by weight of oxypentamethylene thio carbamyl diethyl thio carbamyl sulfide and 2) from about 1% to about 20% by weight of lead naphthenate.

5. A lubricant composition comprising a major proportion of a refined mineral lubricating oil and 1) from about 0.1% to about 3.0% by weight of bis-4-methybenzothiazyl disulfide and (2) from about 1% to about 20% by weight of lead naphthenate.

6. A lubricant composition comprising a major proportion of a refined mineral lubricating oil and 1) from about 0.1% to about 3.0% by weight of benzothiazylgi-butylggiisu}fiile 3nd (Qhfrom about 1% to about 20% References Cited in the file of this patent y Wei 1: 0 ea nap enate.

7. A lubricant composition comprising a major propor- UNITED STATES PATENTS tion of a refined mineral lubricating oil and (1) from 2,154,097 Loane Apr. 11, 1939 about 0.1% to about 3.0% by weight of benzothiazyl- 5 2,218,283 Fuller Oct. 15, 1940 tert-butyl disulfidc and (2) from about 1% to about 20% 2,237,526 Humphreys Apr. 8, 1941 by weight of lead naphthenate. 2,367,355

Kaufman et a1. Jan. 16, 1945 

1. A LUBRICANT COMPOSITION COMPRISING A MAJOR PROPORTION OF A REFINED MINERAL LUBRICATING OIL AND (1) FROM ABOUT 0.1% TO ABOUT 3.0% BY WEIGHT OF A SULFUR- AND NITROGEN-CONTAINING ORGANIC COMPOUND SELECTED FROM THE GROUP CONSISTING OF 2-BENZOTHIAZYL N-N DIETHYL THIO CARBAMYL SULFIDE, 2-BENZOTHIAZYL N-N DIBUTYL THIO CARBAMYL SULFIDE, OXYPENTGAMETHYLENE THIO CARBAMYL DIETHYL THIO CARBAMYL SULFIDE, BIS-4-METHYBENZOTHIAZYL DISULFIDE, BENZOTHIAZYL-N-BUTYL DISULFIDE AND BENZOTHIAZYL-TERT-BUTYL DISULFIDE AND (2) FROM ABOUT 1% TO ABOUT 20% BY WEIGHT OF LEAD NAPHTHENATE. 